The present invention relates to a method and apparatus for the non-invasive detection of certain medical conditions, particularly certain sleep-state conditions, in an individual by monitoring the peripheral vascular system of the individual. The invention also relates to methods and apparatus for aiding in diagnosing the cause of a functional impotence condition, the cause of abrupt changes in the nocturnal glucose level of a diabetic patient, and/or other disorders or conditions in the individual.
PCT Applications No. PCT/IL97/00249 published Feb. 5, 1998 (International Publication No. WO 98/04182); No. PCT/IL99/00292 published Dec. 16, 1999 (WO 99/63884), No. PCT/IL00/00307 published Dec. 14, 2000 (International Publication No. WO 00/74551), No. PCT/IL00/00403 published Jan. 18, 2001 (WO 01/03569), all of which are hereby incorporated by reference as if fully set forth herein, describe non-invasive devices for measuring blood pressure and for detecting various medical conditions, including: myocardial ischemia, certain sleep state conditions, endothelial dysfunction (ED), and stress-induced myocardial ischemia. In the preferred embodiments described in those applications, the described non-invasive devices used volume-measuring sensors and optical sensors for measuring changes in the peripheral arterial bed volume of the individual, which changes were translated to changes in the peripheral arterial tone.
The present application is directed to detecting certain sleep-state conditions, particularly sleep disordered breathing in an individual.
The broad area of sleep disordered breathing encompasses a number of recognized abnormal conditions, including: the obstructive and central sleep apnea syndrome, which results in complete cessations of breathing that occur repeatedly during sleep; obstructive hypopneas, which results in partial upper airway obstruction and reduced ventilation; and the upper airway resistance syndrome (UARS), which results in subtle respiratory changes even though the airflow may appear to be normal. All the foregoing conditions produce frequent awakenings and sleep fragmentation which result in impaired sleep quality and daytime functioning.
Even with the comprehensive battery of measurements used in laboratory based polysomnographic evaluations, the diagnosis of UARS is extremely problematical due to the difficulty in visibly scoring the subtle respiratory changes. [Guilleminault C, Stoohs R, Clark A, Cetel M and Maistros P, “A Cause of Excessive Daytime Sleepiness. The Upper Airway Resistance Syndrome”, Chest 104:781-787 (1993)]. A proper diagnosis of this syndrome necessitates the insertion of an esophageal balloon to measure the patient's intra-thoracic pressure changes. This technique causes great inconvenience and is not well tolerated.
A possible measurable parameter for aiding in the diagnosis of UARS may be the occurrence of frequent cortical or autonomic arousals during sleep. This may be marked by bursts of changes in the electro-encephalographic (EEG) activity, or by bursts of increased sympathetic activation. In many cases, however, there is only increased sympathetic activity with no evidence, or insufficient evidence of cortical arousal in the EEG.
A simple and robust method and apparatus, capable of being used outside the confines of the sleep laboratory for monitoring the sleep state condition, and particularly for marking arousals, would be a very important diagnostic tool in the identification of what might otherwise be an unrecognizable disease state, or in determining the cause of a detected disorder. An example of the latter application described below is in diagnosing the cause of a functional impotence condition in an adult male. Another example described below is in diagnosing and/or treating diabetic conditions of children as well as adults. Further examples are described below particularly applicable to children.
With respect to the impotence application, impotence is the inability of a male to produce or maintain a penile erection such as to enable the male to have sexual intercourse. The condition may stem from organic causes or psychogenic causes. The treatment, therefore, depends to a great extent on the cause. For example, organic causes, such as a small or deformed penis, can frequently be corrected by surgery, whereas other organic causes, such as disease or other disorders, generally require treatment of the disease or disorder causing the condition. On the other hand, where the impotence has a psychogenic basis, the treatment may require the services of a sex therapist or a marriage counselor.
Penile erection, or the lack thereof, during periods of REM sleep have been used to determine whether a patient's impotence may be of an organic or a psychogenic cause. Thus, it has been found that during sleep, normal fluctuations in the autonomic nervous system, which regulates blood flow to the penis, result in periodic, transient penile erections. Such nocturnal erections are substantially unaffected by an erectile dysfunction of a psychogenic origin, but are affected by such a dysfunction which is of an organic nature. A number of penile tumescence and rigidity monitoring devices have been developed and are available for monitoring nocturnal penile erections, as described, for example, in U.S. Pat. Nos. 6,162,188; 4,848,361 and 4,515,166, the contents of which are incorporated herein by reference.
With respect to applications for diagnosing or treating diabetic conditions, it is well known that the risk of hypoglycemia is greater during sleep than during wakefulness. Although the mechanisms underlying this increased risk are unclear, it appears they may be related to blunted counter-regulatory hormonal responses during sleep.
The continuous subcutaneous glucose sensor has been shown to measure glucose levels accurately without causing sleep disruption and allows sampling every five minutes. The subcutaneous continuous glucose determination is however an invasive measurement that requires the surgical insertion of the sensor into the subcutaneous fat of the patient's abdomen. This process is uncomfortable and carries some potential risk. As will be described more particularly below, the novel method and apparatus of the present invention may be used as a non-invasive technique to determine if a diabetic patient is experiencing rapidly changing blood glucose levels during sleep and thereby facilitate the detection of hypoglycemia in diabetic patients during sleep, provided that the patient does not suffer from a concomitant sleep disordered breathing disorder.